1. Field of the Invention
The present invention relates to a semiconductor device, a semiconductor packaging container for implementing semiconductor chip and an electronic device used in a microwave band and a millimeter wave band.
2. Description of the Related Art
Among those semiconductor devices implementing a semiconductor circuit such as an integrated circuit (IC), a large scale integration (LSI) and the like and a semiconductor element such as diode (these are hereinafter referred to as “semiconductor chip”), for those used in a high frequency band, ceramics such as alumina or resin such as epoxy were used as matrix on a mounting substrate. The semiconductor chip is fixed to the mounting substrate with a conductive adhesive. Then, it is sealed with a resin with a gold (Au) wire for wiring. As the resin for sealing, an epoxy based thermosetting resin has been employed in the art.
When using ceramics on the mounting substrate, however, for those used in a high frequency band, it is difficult to make a fine processing. In addition, ceramics itself is so expensive that the cost for manufacturing the semiconductor device cannot be reduced. Further, when using the epoxy based thermosetting resin in the electronic device for a high frequency band such as a microwave band or a millimeter wave band, its relative dielectric constant and dielectric loss causes problems.
For example, for 1 [MHz] band, epoxy has a relative dielectric constant of about 3.8 and a dielectric loss of 0.016, whereas for 1 [GHz] band, epoxy has a relative dielectric constant of about 3.8 and the dielectric loss of 0.080. Therefore, when epoxy is used for the resin for sealing, characteristic impedance of the semiconductor device is changed in the micro wave band and in the millimeter wave band, which makes it impossible to obtain desired electrical characteristics.
From a viewpoint of packaging without influencing the electrical characteristics of the semiconductor chip, it is desirable to make a vacuum ambient environment when the semiconductor chip is mounted, since the relative dielectric constant of vacuum is 1 and the dielectric loss of vacuum is 0. Also, it is desirable to eliminate any reactance change when mounting the semiconductor chip. It is, however, difficult to realize such an ideal ambient environment. Therefore, in order to achieve an ambient as ideal as practical, it is desirable that a semiconductor device has a hollow structure in which resin for sealing is not filled around the semiconductor chip. Also, it is desirable that the semiconductor device is configured so as not to depend on a frequency.
Japanese Patent Laid-open Nos. 63-152156 and 01-215049 disclose a resin sealed semiconductor device having a hollow structure. In such semiconductor devices, packaging container is formed into hollow structure so that the problems in terms of the relative dielectric constant and the dielectric loss in a high frequency band are alleviated. In the semiconductor devices as disclosed in Japanese Patent Laid-open Nos. 63-152156 and 01-215049, however, the semiconductor chip is connected to an external circuit via lead. In such a structure, the inductance increases, due to the lead, in the higher frequency band. Therefore, in a high frequency band of 10 [GHz] or more, increased impedance of a transmission line causes a problem, i.e., the electrical characteristics such as reflection characteristics are deteriorated.
Further, according to a patent document 3 (Japanese Patent Laid-open No. 2002-334944), a semiconductor device having a hollow structure with the use of a resin substrate with shortened leads is disclosed. The semiconductor device as disclosed in the Japanese Patent Laid-open No. 2002-334944, however, is configured such that the leads passes through the inside of resin in the packaging container. This therefore leaves the problem that it is not suitable for use in the millimeter wave of 30 [MHz] or more.